This application proposes to assess the effects of ambient temperature and thyroid hormone levels on the reinforcing effects of 3,4-methylenedioxymethamphetamine (MDMA) in a non-human primate model of drug abuse through methods of intravenous self-administration and in vivo microdialysis. We will compare the reinforcing and hyperthermic effects of self-administered MDMA using a concurrent choice procedure at ambient temperatures of 22 degrees C and 28 degrees C. Also, central dopamine release induced by MDMA within the ventral striatum will be assesed at the previous two ambient temperatures. Finally, the effects of chronic thyroxine treatment on MDMA-induced central dopamine release, hyperthermia and selfadministration will also be evaluated. This proposal aims to elucidate potential mechanisms involved in the reinforcing effects of MDMA and provide a more thorough understanding of the effects of thyroid hormone and ambient temperature on MDMA abuse. Understanding the behavioral and neurochemical mechanisms involved in MDMA-induced reinforcement will allow for increased public awareness and better pharmacotherapies for the toxicities associated with MDMA abuse.